Hi,
What I meant is use a single BBD, like an MN3008 or BL3208 would be great here due to the larger delay than a typical MN3007 et al.
You need at least two LFO's, one slow, one fast. Mix them and use this compound signal to modulate the BBD clock.
Last but not least, mix the dry signal with the delayed signal and you are set.
As an idea, the slow LFO could be sinusoidal, while the faster one could be a filtered squarewave (pseudo triangle) perhaps for a more drammatic effect. YMMV.
As a starting point, you may consider a chorus circuit but with two different LFOs that simoultanueously modulate the BBD Clock IC. A compander on the wet signal might be advisable for optimum noise performance. Again, YMMV.
Cheers.